Cathode ray tube



Sept. 8, 1936.

K. SCHITESINGERJ CA'THODE RAY TUBE Filed Jul 'ls, 1955 @717 2 em for:

Patented Sept. 8, 1936 PATE T OFFICE 2.053.531 CATHODE BAY TUBE Kurt Schlesinger, Berlin, Germany Application July 15, 1933, Serial No. 680,583 In Germany July 19, 1932 2 claims. (CL 250*275) It isknown that in the case of television images reproduced by gas-filled Braun tubes a light co-ordinate cross on a darker ground is always noticeable within the rectangular image held.

5 This cross results from a decrease in the dissociation oi the ions at the moment in which the strength of field between the deflecting plates passes through zero. At this moment the sensitlveness of the tube would appear to be somewhat diminished, the rate of deflection retarded,

and accordingly the density of light increased in the two axial planes. This effect will be referred to in the following as center point error.

It is known that this error in deflection may be overcome by causing theray always to be curved in the plate space, i. e., by avoiding the point E =ii entirely.

Fig. 1 illustrates the conditions. The center point of the image field on the luminous screenan i of the cathode ray tube 2 is taken. to be the point 8. Normally the one plate t is passed togather with the anode 5 on common potential to a straight line from the anode to the screen, i. e.,

is not bent. 30 place.

Now it is obvious and is known that fundamentally. this error may be avoided by the fact that a straight path or the ray is omitted entirely, and the ray enters the plate space in inclined 35 fashion, as indicated by the dotted line 8. In this connection its inclination is suchv that if it were to proceed in a straight line the same, as shown, would be situated outside of the field of image.' In this method, therefore, an addi-- tionai bias-the battery Q-in'Fig. l-will require to be connected in series with the deflecting potential i, which deflects the ray to such extent that the same again falls on the center point 3 45 of the luminous. screen when the alternating po- 1 tential of l passes through 9.

A method has become known in which the oblique entry of the ray into the plate space is accomplished by the fact that the neck of the tube together with the entire ray-generating system and the anode 5 are furnished with a correspondingly inclined position. This method, however, possesses appreciable disadvantages in the manufacture. The angle of deviation of the 55 neck ofthe tube must be performed very ac- Here the center point error takes curately. The production of the tubes in machines is very difiicult if the tubes do not have straight axes, the application of the plates to a common foot of thesystem is dimcult, etc.

The subject matter of the invention refers to t television tubes, which are free from the center point error, and which operate fundamentally with inclined entry of the ray into the plate space, but with the use of special arrangements for the preliminary electrical deflection of the iii ray are so constructed that the axis of the tube remains straight and the entire system central. Additional subject matter of the invention beyond this is constituted by tubes, in which the dimensioning ofthe systems for bending the ray 5 is so performed that one single potential, and accordingly one single lead, is suificient for reliably producing the correct passage of the ray in all bending fields.

The illustration of a simple embodiment of the invention is given in Fig. 2. This system is straight-sighted, but displaced parallel to itself. The ray leaves the anode diaphragm i vertically to the plane of the anode. Its normal path would be the axis 2 of .the tube to the screen 3, which it would strike at its actual center point i. According, however, to the invention, there is provided behind the anode aperture 9. peculiarly constructed box system 5, 6 consisting of two angles. The angle 5 of this system is connected up with the same lead as the anode, i. e., iii-practice to earth. The lead is designated 'i,.and'the connection between 5 and l is shown in rage.

The angle 6 of the box system is situatedion a .bar 8, which possesses a negative potential as compared with the anode bar 71. In consequence the ray will be deflected in space towards the undisturbed axis 2 to the extent of the angle a, The deflection (sis of such extent that the ray would now just strike the lower right hand edge 4% t of the image if no additibnal forces were to act on the same. With this critical inclination, the extent of which is adjustable by the potential at t, the ray enters the actual deflection plate space It) and H, of which a frontalview at A-B is shown in Fig. 4.- The plate M, as usual, is

conducted outwards (preferably by means of the common foot of thetube at a terminal it, with which there is connected on the outside the generator i3, which takes care of the line deflection and is always" dynamically earthed). Generally speaking, therefore; the plate I I possesses the potential of the anode bar I. It is accordingly necessary at the plate In, which is situated opposite thereto, to apply m turn a potential 'which is negative in relation to the anode, so that the ray will be bent back into its old axial direction It and, although with a certain displacement parallel to itself, will again approach the center point of the luminous screen. According to the invention, the deflection sensitivities of the particular co-ordinates of the box system 5, 8 and the main deflecting system l0, II, or l5, ii are selected to be equal to each other. In this case the plate I0 may be connected with the bar 8 in direct fashion, and it is accomplished automatically that the ray again returns to the correct axial position. If the potential at 8 is varied, viz., proceeding from earth potential to a value of approximately 200 volts, there is accordingly not to be observed on the stationary image point 4 anything beyond a slight displacement amounting to perhaps 5-6 mm. in the direction of the one corner of the image. If on the other hand the ray is allowed to pass over the television image screen, there is to be observed upon application of the same measure (varlation of the potential 8) that the disturbing light cross of the center point error moves continuously towards one corner of the image, and finally passes beyond the edge of the picture. In this manner the desired eflect ofrectifying the error has been obtained without varying the sensitiveness of the tube. Merely the image screen has been displaced parallel to itself to the extent of a few millimetres. I

This disadvantage may be avoided by using the form of embodiment of the invention illustrated by way of example in Fig. 3, with two bending condensers and bending of the ray on severaloccasions. In a co-ordinate-the application to the space will be readily understoodthere is shown in Fig. 3 the main model of the tube, followed by a cross-section through a first box system with the plates 2 and 3. The plate 3 is connected with the anode potential bar 4, and the plate 2 on the other hand with a bar having the bending potential I, i. e., with a potential of, for example, 100 volts, which is somewhat negative as compared with the anode and otherwise is capable of regulation. In consequence the ray traverses a parabola with a deflecting angle a in the same manner as if it had proceeded in a straight line from the-center of the plate I at the angle in question. According now to the invention, there follows on the system 2, 3 a system 8, 9 01- plates, possibly of the same dimensions, but twice as long and having reversed polarity. In view of the doubled ratio i d it is accordingly possible to accomplish in the system 8, 9 that the ray reverses its direction in relation to the axis of the tube. The same now behaves in such fashion as if it proceeded from a virtual source of-emission l0. outside or the tube axis, and by varying the potential at 8 it is possible to accomplish that this virtual source is situated more or less eccentrically to the tube axis. As already stated above, the potential 6 is again adjusted in" such fashion that continuation of the new path from Ill in a straightline would be situated .just outside the corner ofthe image. 7

With this inclination the ray enters the actual plate space H, l2, and if in accordance with the invention the sensitivity of all condenser flelds is adjusted to bethe same, it may be accomplished by earthing I! over the defle ting generator l3, and by connection of II with 5, that the ray leaves the entire system with an axis of move ment incidental to that axis of the tube, so that upon the adjustment of the bending potential I there is no change at all in the position of the center point of the image on the screen, whilst at the same time the error cross departs from the field of image.

Owing to the diflerent distances. of the deflecting plates from the anode in the case of series connected condensers, the box condensers must also be spaced differently in the two-co-ordinates, i. e., their cross-sections are not squares, but right angles. Details of this nature, however, do not vary in any way the basic idea of the invention as described, this also apDLVing to an equal extent to the fact that in complicated fashion it is naturally also possible to employ bending systems of diiferent sensitivities it on the other hand for this purpose a corresponding number of diflerent D. C. bending potentials are generated and supthe image co-ordinates and arranged either inplied. It may beparticularly pointed out that side or outside the tube to produce magnetic I transverse fields, which cause the passage of the ray as described, and itis also readily possible, for example by winding and subsequent excitationwith the same current, to fulfill the condition that the amounts of the successive bends again result in the direction of the axis.

I claim: 1

1. Braun tube for television and the like purposes comprising a straight evacuatedenvelope, a gas-filling inside said envelope, a cathode and an anode arranged in operative relationship thereto for producing a cathode ray, means for concentrating the cathode ray, means for controlling the intensity of the cathode ray, a picture receiving screen, scanning means comprising two pairs of deflecting plates for deflecting to a varying degree the cathode ray in two directions vertical to each other for scanning said picture receiving screen, further deflecting means of constant intensity being independent of said deflecting plates and being mounted between said anode and said deflecting plates for causing the my to enter the space between said deflecting plates under an angle to said deflecting Plates, and still further deflecting means causing the ray to prohceed into said picture receiving screen in its original direction after having passed said deflecting plates sytems when said scanning means are out of their operative condition.

2. Braun tube fortelevision and the like purposes comprising a straight evacuated envelope, a gas-filling inside'said envelope, a cathode and an anode arranged in operative relationship thereto for producing a cathode ray, means for concentrating the cathode ray, means for controlling the intensity of the cathode ray, a picture receiving screen, two pairs of deflecting plates for deflecting the cathode ray in two directions vertical to each other for scanning said picture receiving screen, two further plates mounted at right angles to each other between said anode and the first said deflecting plates, and means for connecting one plate of each or said further deflecting plates systems with one plate of one of the first said deflecting plates systems.

xua'r scmsmosa.

pairs of deflecting 

